1. Field of the Invention
The present invention relates to a method for manufacturing a substrate provided with a semiconductor layer with an insulating layer interposed therebetween. In particular the present invention relates to a method for manufacturing an SOI (silicon on insulator) substrate. In addition, the present invention relates to a method for manufacturing a semiconductor device using a substrate provided with a semiconductor layer with an insulating layer interposed therebetween.
2. Description of the Related Art
In recent years, integrated circuits using an SOI substrate where a thin single crystal semiconductor layer is formed on an insulating surface, instead of a bulk silicon wafer, have been developed. Since parasitic capacitance between a drain of a transistor and a substrate is reduced by using the SOI substrate, the SOI substrate has attracted attention as one improving performance of semiconductor integrated circuits.
One of known methods for manufacturing SOI substrates is a Smart Cut (registered trademark) method (for example, see Patent Document 1). An outline of the method for manufacturing an SOI substrate by a Smart Cut method is described below. First, hydrogen ions are implanted into a silicon wafer by an ion-implantation method to form a microbubble layer at a predetermined depth from the surface. Then, the silicon wafer into which the hydrogen ions are implanted is bonded to another silicon wafer with a silicon oxide film interposed therebetween. Then, by heat treatment, the microbubble layer functions as a cleavage plane and a part of the silicon wafer into which hydrogen ions have been implanted is separated in a thin film shape along the microbubble layer. Accordingly, a single crystal silicon film can be formed over the other bonded silicon wafer. A Smart Cut method may also be referred to as a hydrogen-ion-implantation-separation method.
In addition, a method has also been proposed in which a single crystal silicon layer is formed over a base substrate formed of glass by such a Smart Cut method (for example, see Patent Document 2). Since glass substrates can have a larger area and are less expensive than silicon wafers, the glass substrates are mainly used for manufacturing liquid crystal display devices and the like. By using such a glass substrate as a base substrate, a large-sized inexpensive SOI substrate can be manufactured.
Further, a method for irradiating a single crystal silicon layer with a laser beam in order to improve the crystal quality of the single crystal silicon layer is disclosed in Patent Document 2.